The overall objective of this project is to examine the potential role of bacterial mucopeptide in the pathogenesis of rheumatoid arthritis. To this end, we are examining the sera and synovial fluids of patients with rheumatoid arthritis for antibodies to mucopeptide antigens - in particular, those against the immunodominant pentapeptide. Antibodies against the whole mucopeptide were found in many patient groups and normals, and the sera of patients with rheumatoid arthritis were not significantly different. Therefore, we are isolating the peptide-containing portion of the mucopeptide in order to screen the sera and synovial fluids for the presence of antibodies.